Unless you want to go craigslist hunting, there aren't many "real" 2.1 options for $100. You'd be able to get a decent set of computer speakers for that much though. What sources do you want to hook up to? Just the TV's internal tuner? Cable box? Something else?
Do your sources have analog audio outputs?
I'd say welcome to AT, but it looks like you've been here almost as long as I have.
http://pics.bbzzdd.com/users/YOyoYOhowsDAjello/Welcome2.JPG